Torque of an internal combustion engine may be adjusted via adjusting engine air flow, an amount of fuel delivered to the engine, and adjusting engine spark timing. Engine spark timing may be empirically determined and stored in tables or functions in memory of a controller. Spark timing may be adjusted as engine speed and load change to provide a higher level of engine efficiency and avoid engine knock. In addition, spark timing may be reduced from time to time to reduce engine torque since engine torque may be reduced more quickly via spark timing than via adjusting engine air flow. For example, engine spark timing may be retarded from minimum spark timing for best engine torque (MBT) timing during a gear shift of a dual clutch transmission so that engine speed may be synchronized with transmission input shaft speed during an upshift. If spark timing adjustments are not well correlated to a desired engine torque reduction or increase, engine speed during the shift will not match transmission input shaft speed. If engine speed does not match transmission input shaft speed, clutch slip and degradation may increase. In addition, transmission shift feel may degrade.
The inventors herein have recognized the above-mentioned issues and have developed a driveline operating method, comprising: maintaining an engine at idle speed and operating the engine in a torque control mode while input clutches of a transmission are open in response to a request to adapt values of an engine spark to engine torque relationship, the engine positioned upstream of the input clutches; adjusting the values responsive to engine torque while maintaining the engine at idle speed; and operating the engine responsive to the values.
By maintaining an engine at idle speed and operating the engine in a torque control mode while input clutches of a transmission are open in response to a request to adapt values of an engine spark to torque relationship, and adjusting the values responsive to engine torque while maintaining the engine idle speed, it may be possible to adapt engine spark timing so that an engine provides a desired amount of torque. In one example, engine speed is maintained at engine idle speed via an integrated starter/generator while the engine operates in a torque control mode. The engine output torque may be determined via ISG current so that engine spark timing values that provides a desired amount of engine torque may be adjusted. The engine spark to engine torque relationship values may be adjusted responsive to engine torque and engine spark timing values during a period when the engine is not propelling a vehicle so that adaptation may not be noticeable to vehicle occupants. The adaptation of engine spark to engine torque values may be based on steady-state and dynamic vehicle operating conditions.
The present description may provide several advantages. Specifically, the approach may improve efficiency vehicle drivability. Further, the approach may improve vehicle drivability without having to disturb vehicle occupants. Further still, the approach may reduce driveline torque disturbances and driveline component degradation.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.